Conventional roof mounted solar collector devices are generally complex, bulky and expensive, and generally use circulating liquids which are heated by the solar radiation. These systems have problems due to potential freezing and leaks.
Present air heat collectors are bulky and are not generally used for large scale heat collection. Consequently, liquid cooled collectors are generally used.
Present air type collectors use a flat channel, one side of which is glazed with usually double glazing, and the opposite flat side is black and heats the air passing through the collector.
Because the air passes against the glazing, heat is lost unless double glazing is used and this is expensive and troublesome.
Installation is likewise troublesome and the units are bulky.